Fix escaping of interpolated arguments in markup

[GrantTotinov]

Fixes #1763

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• All newly added code is adequately covered by tests
• All existing tests are still running without errors

Changes

Previously, only string arguments were escaped in Markup.EscapeInterpolated.

This caused runtime crashes when non-string objects were interpolated and their ToString() output contained markup-sensitive characters (e.g. square brackets), which were then interpreted as markup.

This change ensures that all interpolated arguments are consistently converted to string and escaped before formatting, preventing unintended markup parsing and runtime exceptions.

A regression test was added for objects whose ToString() contains square brackets.

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[patriksvensson]

LGTM 👍